include/boost/corosio/native/detail/reactor/reactor_descriptor_state.hpp
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boost::corosio::detail::reactor_descriptor_state::add_ready_events(unsigned int)
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boost::corosio::detail::reactor_descriptor_state::operator()()
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boost::corosio::detail::reactor_descriptor_state::destroy()
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boost::corosio::detail::reactor_descriptor_state::invoke_deferred_io()
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| Line | TLA | Hits | Source Code |
|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2026 Steve Gerbino | ||
| 3 | // | ||
| 4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 6 | // | ||
| 7 | // Official repository: https://github.com/cppalliance/corosio | ||
| 8 | // | ||
| 9 | |||
| 10 | #ifndef BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_DESCRIPTOR_STATE_HPP | ||
| 11 | #define BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_DESCRIPTOR_STATE_HPP | ||
| 12 | |||
| 13 | #include <boost/corosio/native/detail/reactor/reactor_events.hpp> | ||
| 14 | #include <boost/corosio/native/detail/reactor/reactor_op_base.hpp> | ||
| 15 | #include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp> | ||
| 16 | #include <boost/corosio/detail/ready_queue.hpp> | ||
| 17 | |||
| 18 | #include <boost/corosio/detail/conditionally_enabled_mutex.hpp> | ||
| 19 | |||
| 20 | #include <atomic> | ||
| 21 | #include <cstdint> | ||
| 22 | #include <memory> | ||
| 23 | |||
| 24 | #include <errno.h> | ||
| 25 | #include <sys/socket.h> | ||
| 26 | |||
| 27 | namespace boost::corosio::detail { | ||
| 28 | |||
| 29 | /** Per-descriptor state shared across reactor backends. | ||
| 30 | |||
| 31 | Tracks pending operations for a file descriptor. The fd is registered | ||
| 32 | once with the reactor and stays registered until closed. Uses deferred | ||
| 33 | I/O: the reactor sets ready_events atomically, then enqueues this state. | ||
| 34 | When popped by the scheduler, invoke_deferred_io() performs I/O under | ||
| 35 | the mutex and queues completed ops. | ||
| 36 | |||
| 37 | Non-template: uses reactor_op_base pointers so the scheduler and | ||
| 38 | descriptor_state code exist as a single copy in the binary regardless | ||
| 39 | of how many backends are compiled in. | ||
| 40 | |||
| 41 | @par Thread Safety | ||
| 42 | The mutex protects operation pointers and ready flags. ready_events_ | ||
| 43 | and is_enqueued_ are atomic for lock-free reactor access. | ||
| 44 | */ | ||
| 45 | struct reactor_descriptor_state : scheduler_op | ||
| 46 | { | ||
| 47 | /// Protects operation pointers and ready/cancel flags. | ||
| 48 | /// Becomes a no-op in single-threaded mode. | ||
| 49 | conditionally_enabled_mutex mutex{true}; | ||
| 50 | |||
| 51 | /// Pending read operation (guarded by `mutex`). | ||
| 52 | reactor_op_base* read_op = nullptr; | ||
| 53 | |||
| 54 | /// Pending write operation (guarded by `mutex`). | ||
| 55 | reactor_op_base* write_op = nullptr; | ||
| 56 | |||
| 57 | /// Pending connect operation (guarded by `mutex`). | ||
| 58 | reactor_op_base* connect_op = nullptr; | ||
| 59 | |||
| 60 | /// Pending wait-for-read operation (guarded by `mutex`). | ||
| 61 | reactor_op_base* wait_read_op = nullptr; | ||
| 62 | |||
| 63 | /// Pending wait-for-write operation (guarded by `mutex`). | ||
| 64 | reactor_op_base* wait_write_op = nullptr; | ||
| 65 | |||
| 66 | /// Pending wait-for-error operation (guarded by `mutex`). | ||
| 67 | reactor_op_base* wait_error_op = nullptr; | ||
| 68 | |||
| 69 | /// True if a read edge event arrived before an op was registered. | ||
| 70 | bool read_ready = false; | ||
| 71 | |||
| 72 | /// True if a write edge event arrived before an op was registered. | ||
| 73 | bool write_ready = false; | ||
| 74 | |||
| 75 | /// Event mask set during registration (no mutex needed). | ||
| 76 | std::uint32_t registered_events = 0; | ||
| 77 | |||
| 78 | /// File descriptor this state tracks. | ||
| 79 | int fd = -1; | ||
| 80 | |||
| 81 | /// Accumulated ready events (set by reactor, read by scheduler). | ||
| 82 | std::atomic<std::uint32_t> ready_events_{0}; | ||
| 83 | |||
| 84 | /// True while this state is queued in the scheduler's completed_ops. | ||
| 85 | std::atomic<bool> is_enqueued_{false}; | ||
| 86 | |||
| 87 | /// Owning scheduler for posting completions. | ||
| 88 | reactor_scheduler const* scheduler_ = nullptr; | ||
| 89 | |||
| 90 | /// Prevents impl destruction while queued in the scheduler. | ||
| 91 | std::shared_ptr<void> impl_ref_; | ||
| 92 | |||
| 93 | /// Add ready events atomically. | ||
| 94 | /// Release pairs with the consumer's acquire exchange on | ||
| 95 | /// ready_events_ so the consumer sees all flags. On x86 (TSO) | ||
| 96 | /// this compiles to the same LOCK OR as relaxed. | ||
| 97 | 379348x | void add_ready_events(std::uint32_t ev) noexcept | |
| 98 | { | ||
| 99 | 379348x | ready_events_.fetch_or(ev, std::memory_order_release); | |
| 100 | 379348x | } | |
| 101 | |||
| 102 | /// Invoke deferred I/O and dispatch completions. | ||
| 103 | 379058x | void operator()() override | |
| 104 | { | ||
| 105 | 379058x | invoke_deferred_io(); | |
| 106 | 379058x | } | |
| 107 | |||
| 108 | /// Destroy without invoking. | ||
| 109 | /// Called during scheduler::shutdown() drain. Clear impl_ref_ to break | ||
| 110 | /// the self-referential cycle set by close_socket(). | ||
| 111 | 290x | void destroy() override | |
| 112 | { | ||
| 113 | 290x | impl_ref_.reset(); | |
| 114 | 290x | } | |
| 115 | |||
| 116 | /** Perform deferred I/O and queue completions. | ||
| 117 | |||
| 118 | Performs I/O under the mutex and queues completed ops. EAGAIN | ||
| 119 | ops stay parked in their slot for re-delivery on the next | ||
| 120 | edge event. | ||
| 121 | */ | ||
| 122 | void invoke_deferred_io(); | ||
| 123 | }; | ||
| 124 | |||
| 125 | inline void | ||
| 126 | 379058x | reactor_descriptor_state::invoke_deferred_io() | |
| 127 | { | ||
| 128 | 379058x | std::shared_ptr<void> prevent_impl_destruction; | |
| 129 | 379058x | ready_queue local_ops; | |
| 130 | |||
| 131 | { | ||
| 132 | 379058x | conditionally_enabled_mutex::scoped_lock lock(mutex); | |
| 133 | |||
| 134 | // Must clear is_enqueued_ and move impl_ref_ under the same | ||
| 135 | // lock that processes I/O. close_socket() checks is_enqueued_ | ||
| 136 | // under this mutex — without atomicity between the flag store | ||
| 137 | // and the ref move, close_socket() could see is_enqueued_==false, | ||
| 138 | // skip setting impl_ref_, and destroy the impl under us. | ||
| 139 | 379058x | prevent_impl_destruction = std::move(impl_ref_); | |
| 140 | 379058x | is_enqueued_.store(false, std::memory_order_release); | |
| 141 | |||
| 142 | 379058x | std::uint32_t ev = ready_events_.exchange(0, std::memory_order_acquire); | |
| 143 | 379058x | if (ev == 0) | |
| 144 | { | ||
| 145 | // Mutex unlocks here; compensate for work_cleanup's decrement | ||
| 146 | 4x | scheduler_->compensating_work_started(); | |
| 147 | 4x | return; | |
| 148 | } | ||
| 149 | |||
| 150 | 379054x | int err = 0; | |
| 151 | 379054x | if (ev & reactor_event_error) | |
| 152 | { | ||
| 153 | 32x | socklen_t len = sizeof(err); | |
| 154 | 32x | if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &len) < 0) | |
| 155 | 10x | err = errno; | |
| 156 | // select raises its exceptional set for out-of-band/urgent | ||
| 157 | // data as well as for genuine faults; on a healthy socket the | ||
| 158 | // probe then reads SO_ERROR == 0. Faulting a pending read or | ||
| 159 | // write on that is wrong, so an I/O operation completes only | ||
| 160 | // on a real (non-zero) error. wait(error) still names a code | ||
| 161 | // below. | ||
| 162 | } | ||
| 163 | |||
| 164 | 379054x | if (ev & reactor_event_read) | |
| 165 | { | ||
| 166 | 352319x | if (read_op) | |
| 167 | { | ||
| 168 | 7393x | auto* rd = read_op; | |
| 169 | 7393x | if (err) | |
| 170 | 3x | rd->complete(err, 0); | |
| 171 | else | ||
| 172 | 7390x | rd->perform_io(); | |
| 173 | |||
| 174 | 7393x | if (rd->errn == EAGAIN || rd->errn == EWOULDBLOCK) | |
| 175 | { | ||
| 176 | 360x | rd->errn = 0; | |
| 177 | } | ||
| 178 | else | ||
| 179 | { | ||
| 180 | 7033x | read_op = nullptr; | |
| 181 | 7033x | local_ops.push(rd); | |
| 182 | } | ||
| 183 | } | ||
| 184 | else | ||
| 185 | { | ||
| 186 | 344926x | read_ready = true; | |
| 187 | } | ||
| 188 | |||
| 189 | // The event does not prove the socket is still readable: a | ||
| 190 | // parked read op above may have drained it, or a speculative | ||
| 191 | // read consumed the data before this dispatch ran. The wait | ||
| 192 | // op's perform_io() re-probes and reports EAGAIN to stay | ||
| 193 | // parked. | ||
| 194 | 352319x | if (wait_read_op) | |
| 195 | { | ||
| 196 | 27x | auto* wo = wait_read_op; | |
| 197 | 27x | if (err) | |
| 198 | 1x | wo->complete(err, 0); | |
| 199 | else | ||
| 200 | 26x | wo->perform_io(); | |
| 201 | |||
| 202 | 27x | if (wo->errn == EAGAIN || wo->errn == EWOULDBLOCK) | |
| 203 | { | ||
| 204 | 4x | wo->errn = 0; | |
| 205 | } | ||
| 206 | else | ||
| 207 | { | ||
| 208 | 23x | wait_read_op = nullptr; | |
| 209 | 23x | local_ops.push(wo); | |
| 210 | } | ||
| 211 | } | ||
| 212 | } | ||
| 213 | 379054x | if (ev & reactor_event_write) | |
| 214 | { | ||
| 215 | 35883x | bool had_write_op = (connect_op || write_op); | |
| 216 | // A writable event on a socket still in SYN_SENT (e.g. the | ||
| 217 | // spurious pre-connect readiness of a fresh socket) must | ||
| 218 | // not complete the connect; perform_io() reports EAGAIN | ||
| 219 | // until a peer is actually established. | ||
| 220 | 35883x | if (connect_op) | |
| 221 | { | ||
| 222 | 6562x | auto* cn = connect_op; | |
| 223 | 6562x | if (err) | |
| 224 | 8x | cn->complete(err, 0); | |
| 225 | else | ||
| 226 | 6554x | cn->perform_io(); | |
| 227 | |||
| 228 | 6562x | if (cn->errn == EAGAIN || cn->errn == EWOULDBLOCK) | |
| 229 | { | ||
| 230 | ✗ | cn->errn = 0; | |
| 231 | } | ||
| 232 | else | ||
| 233 | { | ||
| 234 | 6562x | connect_op = nullptr; | |
| 235 | 6562x | local_ops.push(cn); | |
| 236 | } | ||
| 237 | } | ||
| 238 | 35883x | if (write_op) | |
| 239 | { | ||
| 240 | 196x | auto* wr = write_op; | |
| 241 | 196x | if (err) | |
| 242 | 2x | wr->complete(err, 0); | |
| 243 | else | ||
| 244 | 194x | wr->perform_io(); | |
| 245 | |||
| 246 | 196x | if (wr->errn == EAGAIN || wr->errn == EWOULDBLOCK) | |
| 247 | { | ||
| 248 | 1x | wr->errn = 0; | |
| 249 | } | ||
| 250 | else | ||
| 251 | { | ||
| 252 | 195x | write_op = nullptr; | |
| 253 | 195x | local_ops.push(wr); | |
| 254 | } | ||
| 255 | } | ||
| 256 | 35883x | if (!had_write_op) | |
| 257 | 29125x | write_ready = true; | |
| 258 | |||
| 259 | // Same re-probe discipline as the wait-for-read dispatch. | ||
| 260 | 35883x | if (wait_write_op) | |
| 261 | { | ||
| 262 | 7x | auto* wo = wait_write_op; | |
| 263 | 7x | if (err) | |
| 264 | 2x | wo->complete(err, 0); | |
| 265 | else | ||
| 266 | 5x | wo->perform_io(); | |
| 267 | |||
| 268 | 7x | if (wo->errn == EAGAIN || wo->errn == EWOULDBLOCK) | |
| 269 | { | ||
| 270 | ✗ | wo->errn = 0; | |
| 271 | } | ||
| 272 | else | ||
| 273 | { | ||
| 274 | 7x | wait_write_op = nullptr; | |
| 275 | 7x | local_ops.push(wo); | |
| 276 | } | ||
| 277 | } | ||
| 278 | } | ||
| 279 | // Complete a parked wait-for-error on any error condition. | ||
| 280 | 379054x | if ((ev & reactor_event_error) || err) | |
| 281 | { | ||
| 282 | 32x | if (wait_error_op) | |
| 283 | { | ||
| 284 | // wait(error) fired on the exceptional condition; name a | ||
| 285 | // code even when the kernel exposed none (e.g. urgent | ||
| 286 | // data leaves SO_ERROR == 0). | ||
| 287 | 3x | int const werr = err ? err : EIO; | |
| 288 | 3x | wait_error_op->complete(werr, 0); | |
| 289 | 3x | local_ops.push(std::exchange(wait_error_op, nullptr)); | |
| 290 | } | ||
| 291 | } | ||
| 292 | 379054x | if (err) | |
| 293 | { | ||
| 294 | 27x | if (read_op) | |
| 295 | { | ||
| 296 | 1x | read_op->complete(err, 0); | |
| 297 | 1x | local_ops.push(std::exchange(read_op, nullptr)); | |
| 298 | } | ||
| 299 | 27x | if (write_op) | |
| 300 | { | ||
| 301 | ✗ | write_op->complete(err, 0); | |
| 302 | ✗ | local_ops.push(std::exchange(write_op, nullptr)); | |
| 303 | } | ||
| 304 | 27x | if (connect_op) | |
| 305 | { | ||
| 306 | ✗ | connect_op->complete(err, 0); | |
| 307 | ✗ | local_ops.push(std::exchange(connect_op, nullptr)); | |
| 308 | } | ||
| 309 | 27x | if (wait_read_op) | |
| 310 | { | ||
| 311 | 1x | wait_read_op->complete(err, 0); | |
| 312 | 1x | local_ops.push(std::exchange(wait_read_op, nullptr)); | |
| 313 | } | ||
| 314 | 27x | if (wait_write_op) | |
| 315 | { | ||
| 316 | ✗ | wait_write_op->complete(err, 0); | |
| 317 | ✗ | local_ops.push(std::exchange(wait_write_op, nullptr)); | |
| 318 | } | ||
| 319 | } | ||
| 320 | 379058x | } | |
| 321 | |||
| 322 | // Execute first handler inline — the scheduler's work_cleanup | ||
| 323 | // accounts for this as the "consumed" work item. local_ops holds | ||
| 324 | // only ops, so the popped entry decodes directly. | ||
| 325 | 379054x | scheduler_op* first = ready_as_op(local_ops.pop()); | |
| 326 | 379054x | if (first) | |
| 327 | { | ||
| 328 | 13823x | scheduler_->post_deferred_completions(local_ops); | |
| 329 | 13823x | (*first)(); | |
| 330 | } | ||
| 331 | else | ||
| 332 | { | ||
| 333 | 365231x | scheduler_->compensating_work_started(); | |
| 334 | } | ||
| 335 | 379058x | } | |
| 336 | |||
| 337 | } // namespace boost::corosio::detail | ||
| 338 | |||
| 339 | #endif // BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_DESCRIPTOR_STATE_HPP | ||
| 340 |